“If you don’t vote,” goes the old saying, “don’t gripe.”

In a typical primary election, even during a presidential year like this one, hordes of registered voters in our state don’t bother to cast their ballots, though they may reserve the right to gripe later about the results.

Much of the traditional primary apathy can be traced to one factor: North Carolina schedules its primary so late in the season as to render the presidential vote meaningless.

This time around, Republican voters can go through the motions of choosing among Newt Gingrich, Ron Paul, Mitt Romney, Rick Santorum or No Preference. But for better or worse, the fact is that results in other electoral battlegrounds have already effectively determined the nominee: Romney. The pickings are even slimmer on the Democratic side: It’s Barack Obama or nobody. Those trains have left the station.

But never mind the seeming presidential pointlessness at the top of the ballot. There are still plenty of important reasons from there on down to make sure you participate in the small-“d” democratic process — assuming you haven’t already taken advantage of the early-voting option.

The question likely to produce a big spike in Tuesday’s turnout comes not at the top of the ballot but at its very bottom. It reads like this: “Constitutional amendment to provide that marriage between one man and one woman is the only domestic legal union that shall be valid or recognized in this state.”

You may wonder why that decision is even being sought at this particular time. Pilot reader Richard Siege did, emailing this question to us early Friday: “Why has such an important issue as the ‘Marriage Amendment’ been placed on the ballot in the primary election instead of its proper place, the general election?”

Good question. Republican sponsors say they just want to get the question out there as soon as possible. Democrats charge that the timing is an effort to drive up the margin of “for” votes, since there are more contested races on the Republican ballot than on the Democratic one, assuring a higher turnout of GOP voters.

In any case, it is important that voters not be confused by the wording of the question, as at least a few seem to have been here and there. In effect, voting “for” the amendment means voting against state recognition of gay marriages or domestic unions. Voting “against” the amendment means the voter does not think the state constitution should be modified by adding this definition of what constitutes officially valid marriages or domestic unions.

However you choose to vote on these or other questions, the important thing is that you vote.